Absorptive coding metasurface with ultrawideband backscattering reduction

Abstract

In this letter, a new absorptive coding metasurface with a triple-layer topology is proposed to reduce the backscattering in an ultrawide band by combining absorption and diffusion simultaneously. Two separate layers for the coding metasurface and absorber are designed to primarily reduce the high- and low-frequency backscattering. A high-frequency reflective frequency selective surface is added between the coding metasurface and the absorber, serving as an equivalent ground plane for the coding metasurface and eliminating the adverse influence of the harmonic resonances of the absorber at high frequencies. The proposed absorptive coding metasurface is very robust for absorption and diffusion, resulting in a backscattering reduction over an ultrawide band. To validate the concept, an absorptive coding metasurface with a size of 288 mm × 288 mm is designed. Its unit cell exhibits a copolarized reflection magnitude smaller than -10 dB from 1.55 to 19.2 GHz (corresponding bandwidth ratio (BWR) of 1:12.4) with a thickness of 17.73 mm (about 0.092λL at the lowest operating frequency). Simulated and measured results of the absorptive coding metasurface are in good agreement, and they demonstrate a significant backscattering reduction from 1.85 to 19.2 GHz in comparison with a metallic plane of the same size.